It looks like you have custom styles set on your popup, given it looks different from the defaults. I'd suggest these are the culprits here, as the default styles are fine:
Simplest way to check is to look in the browser's dev tools at that popup, and see what styles are on various levels relating to it in the DOM
I'd be looking to see if overflow: hidden is set on this classed DOM element:
Note: the overflow for yours will not be set on the "element.style", it will be part of another rule; I added this manually via the dev tools.
If you go to the "Computed" tab and look for "overflow" you can then click on the link beside it on the to nav to the rule that defines it:
If the rule is defined within the stylesheet, it will appear something like this:
Apologies for the scribbles...